Salts of treprostinil

ABSTRACT

Provided are novel treprostinil salts as well as methods for making treprostinil salts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.16/399,682, filed Apr. 30, 2019, which is a Continuation of U.S.application Ser. No. 15/995,372, filed Jun. 1, 2018, which is aContinuation of U.S. application Ser. No. 15/614,801, filed Jun. 6,2017, now U.S. Pat. No. 9,988,334, which is a Continuation of U.S.application Ser. No. 15/359,941, filed Nov. 23, 2016, now U.S. Pat. No.9,701,611, which is a Continuation of U.S. application Ser. No.14/634,131, filed Feb. 27, 2015, which is a Continuation of U.S.application Ser. No. 14/202,618, filed Mar. 10, 2014, now abandoned,which claims the benefit under 35 U.S.C. § 119(e) of U.S. ProvisionalApplication No. 61/791,015, filed on Mar. 15, 2013, the contents ofwhich are hereby incorporated by reference in their entirety into thepresent disclosure.

BACKGROUND

Treprostinil, the active ingredient in Remodulin®, Tyvaso® andOrenitram™, was first described in U.S. Pat. No. 4,306,075.Treprostinil, and other prostacyclin derivatives may be prepared asdescribed in Moriarty, et al in J. Org. Chem. 2004, 69, 1890-1902, Drugof the Future, 2001, 26(4), 364-374, U.S. Pat. Nos. 6,441,245,6,528,688, 6,700,025, 6,809,223, 6,756,117; 8,461,393; 8,481,782;8,242,305; 8,497,393; US patent applications nos. 2012-0190888 and2012-0197041; PCT publication no. WO2012/009816.

Various uses and/or various forms of treprostinil are disclosed, forexamples, in U.S. Pat. Nos. 5,153,222; 5,234,953; 6,521,212; 6,756,033;6,803,386; 7,199,157; 6,054,486; 7,417,070; 7,384,978; 7,879,909;8,563,614; 8,252,839; 8,536,363; 8,410,169; 8,232,316; 8,609,728;8,350,079; 8,349,892; 7,999,007; 8,658,694; 8,653,137; US patentapplication publications nos. 2005/0165111; 2009/0036465; 2008/0200449;2010-0076083; 2012-0216801; 2008/0280986; 2009-0124697; 2013-0261187;PCT publication no. WO00/57701; US provisional applications nos.61/781,303 filed Mar. 14, 2013 and 61/805,048 filed Mar. 25, 2013. Theteachings of the aforementioned references are incorporated by referenceto show how to practice the embodiments of the present invention.

The teachings of the aforementioned references are incorporated byreference to show how to practice the embodiments of the presentinvention. The methods described in these documents, however, do notdescribe a feasible production method for producing salts oftreprostinil because the methods require the use of excessive amounts ofreagents and tedious chromatographic purification techniques. Therefore,there is a need for an economical, efficient and simplified method forpreparing salts of treprostinil.

In sum, treprostinil is of great importance from a medicinal point ofview. Therefore, a need exists for stable forms of treprostinil whichpresents advantage in storage, shipment, handling, and/or formulation,for example. From synthetic point of view, the desired properties ofUT-15 salts may include one or more of the following properties: betteraqueous solubility, higher melting point, dense nature, and robustprocess.

SUMMARY

Certain embodiments of the present invention relate to methods ofpreparing various salts of treprostinil.

One embodiment provides a treprostinil salt compound according to thefollowing formula:

that may be optionally produced by a process comprising: alkylating astarting compound of the formula:

to form an O-alkylated compound that is not isolated; followed byoptional base hydrolysis and contacting the resulting compound with abase or a base salt in situ; wherein X is a pharmaceutically acceptablesalt counterion and the treprostinil salt is isolated as at least 98%pure. In one embodiment, the treprostinil salt comprises Group IA or IIAmetal. In another embodiment, the treprostinil salt comprises K, Ca, Na,Ba, Li, Mg, or Cs. In yet another embodiment, the treprostinil salt asisolated is at least 98.5% pure; at least 98.8% pure; at least 99% pure;at least 99.1% pure; at least 99.2% pure; at least 99.3% pure; at least99.4% pure; at least 99.5% pure; at least 99.6% pure; at least 99.7%pure; at least 99.8% pure or at least 99.9% pure.

One embodiment provides a treprostinil salt compound according to thefollowing formula:

wherein X is a pharmaceutically acceptable salt counterion and thetreprostinil salt is isolated preferably in a crystalline form.Preferably, the isolated salt is at least 99% pure. In one embodiment,the treprostinil salt comprises a Group IA or IIA metal. In anotherembodiment, the treprostinil salt comprises K, Ca, Na, Ba, Li, Mg or Cs.In yet another embodiment, the treprostinil salt as isolated is at least99.1% pure; at least 99.2% pure; at least 99.3% pure; at least 99.4%pure; at least 99.5% pure; at least 99.6% pure; at least 99.7% pure; atleast 99.8% pure or at least 99.9% pure or at least 99.95% pure.

One embodiment provides a treprostinil salt compound according to thefollowing formula:

that may be optionally produced by a process comprising: alkylating astarting compound of the formula:

to form an O-alkylated compound that is not isolated; followed byhydrogenolysis and contacting the resulting compound with a base or abase salt in situ; wherein X is a pharmaceutically acceptable saltcounterion and the treprostinil salt is isolated as at least 98% pure.In one embodiment, the treprostinil salt comprises a Group IA or IIAmetal. In another embodiment, the treprostinil salt comprises K, Ca, Na,Ba, Li, Mg or Cs. In yet another embodiment, the treprostinil salt asisolated is at least 98.5% pure; at least 98.8% pure; at least 99% pure;at least 99.1% pure; at least 99.2% pure; at least 99.3% pure; at least99.4% pure; at least 99.5% pure; at least 99.6% pure; at least 99.7%pure; at least 99.8% pure or at least 99.9% pure.

Another embodiment provides a method for making a treprostinil saltcompound according to the following formula:

comprising alkylating a starting compound of the formula:

to form an O-alkylated compound that is not isolated; followed byoptional base hydrolysis and contacting the resulting compound with abase or a base salt in situ; wherein X is a pharmaceutically acceptablesalt counterion and the treprostinil salt is isolated as at least 98%pure. In one embodiment, the treprostinil salt comprises a Group IA orIIA metal. In another embodiment, the treprostinil salt comprises K, Ca,Na, Ba, Li, Mg or Cs. In yet another embodiment, the treprostinil saltas isolated is at least 98.5% pure; at least 98.8% pure; at least 99%pure; at least 99.1% pure; at least 99.2% pure; at least 99.3% pure; atleast 99.4% pure; at least 99.5% pure; at least 99.6% pure; at least99.7% pure; at least 99.8% pure or at least 99.9% pure.

Yet another embodiment provides a method for making a treprostinil saltcompound according to the following formula:

comprising alkylating a starting compound of the formula:

to form an O-alkylated compound that is not isolated; followed byhydrogenolysis and contacting the resulting compound with a base or abase salt in situ; wherein X is a pharmaceutically acceptable saltcounterion and the treprostinil salt is isolated as at least 98% pure.In one embodiment, the treprostinil salt comprises a Group IA or IIAmetal. In another embodiment, the treprostinil salt comprises K, Ca, Na,Ba, Li, Mg or Cs. In yet another embodiment, the treprostinil salt asisolated is at least 98.5% pure; at least 98.8% pure; at least 99% pure;at least 99.1% pure; at least 99.2% pure; at least 99.3% pure; at least99.4% pure; at least 99.5% pure; at least 99.6% pure; at least 99.7%pure; at least 99.8% pure or at least 99.9% pure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows embodiments of exemplary synthetic pathways which result intreprostinil salt. In FIG. 1 each of R1 and R2 may be independentlyselected from H or an alcohol protecting group, such as H, TBDMS, THP,substituted or unsubstituted benzyl group. Exemplary alcohol protectinggroups include, but are not limited to, actetyl, benzoyl, benzyl,p-methoxyethoxymethyl ether, methoxymethyl ether, dimethoxytrityl,p-methoxybenzyl ether, trityl, silyl ether (e.g., trimethylsilyl (TMS),tert-butyldimethylsilyl (TBMDS), tert-butyldimethylsilyloxymethyl (TOM)or triisopropylsilyl (TIPS) ether), tetrahydropyranyl (THP), methylether and ethoxyethyl ether (EE).

FIG. 2 is chart representing the relationship between yield and theacetone/ethanol ratio.

FIG. 3 is chart representing the relationship between yield and theethyl acetate/ethanol ratio.

FIG. 4 is a flow chart for synthesis of salts of UT-15 and UT-15starting from triol.

DETAILED DESCRIPTION

Unless otherwise specified, “a” or “an” means “one or more”. The presentinvention relates to a novel monohydrate form of treprostinil.Treprostinil is the active ingredient of Remodulin®, which has beenapproved by the U.S. FDA for the treatment of Pulmonary ArterialHypertension (PAH) in patients with NYHA Class II, III and IV symptomsto diminish symptoms associated with exercise using subcutaneous orintravenous administration. Treprostinil is also the active ingredientin Tyvaso® inhalation solution and Orenitram™ extended-release tablets.

Treprostinil's chemical name is2-((1R,2R,3aS,9aS)-2-hydroxy-1-((S)-3-hydroxyoctyl)-2,3,3a,4,9,9a-hexahydro-1H-cyclopenta[b]naphthalen-5-yloxy)aceticacid of the following structure:

Treprostinil (UT-15) is a benzindene prostacyclin containing carboxylicacid functionality, various bases and base salts may react with the acidfunctionality to form new salts of treprostinil as shown in FIG. 1. Insome embodiments, a hydroxide base, such as alkaline metal hydroxide,may be reacted with treprostinil or a synthetic intermediate oftreprostinil to form a salt of treprostinil. The hydroxide base may be,for example, an inorganic base such as ammonium hydroxide, potassiumhydroxide, calcium hydroxide, sodium hydroxide, barium hydroxide, cesiumhydroxide, lithium hydroxide and magnesium hydroxide. The resulting saltmay be, for example, Potassium, Calcium, Sodium, Barium, Lithium,Magnesium or Cesium salt. Yet in some embodiments, a base salt, such asa carbonate, may be reacted with treprostinil or a syntheticintermediate of treprostinil to form a salt of treprostinil. Thecarbonate may be, for example, lithium carbonate, potassium carbonate,sodium carbonate, cesium carbonate, calcium carbonate, ammoniumcarbonate.

Additional salts may be used according to the processes embodied herein,including for example, compounds with basic groups, such as aminegroups, basic salts include ammonium salts, alkali metal salts (such assodium, potassium and cesium salts) and alkaline earth metal salts (suchas magnesium, calcium and barium salts).

One embodiment includes synthesis of a form new salt of treprostinil byany of the following methods. In some embodiments, the synthesis of saltmay be a two step process starting from compound of formula (1)

wherein each of R1 and R2 may be independently selected from H or analcohol protecting group, such as H, TBDMS, THP, substituted orunsubstituted benzyl group. As used herein, “an alcohol protectinggroup” is a functional group that protects the alcohol group fromparticipating in reactions that are occurring in other parts of themolecule. Suitable alcohol protecting groups are well known to those ofordinary skill in the art and include those found in T. W. Greene,Protecting Groups in Organic Synthesis, John Wiley & Sons, Inc. 1981,the entire teachings of which are incorporated herein by reference.Exemplary alcohol protecting groups include, but are not limited to,actetyl, benzoyl, benzyl, p-methoxyethoxymethyl ether, methoxymethylether, dimethoxytrityl, p-methoxybenzyl ether, trityl, silyl ether(e.g., trimethylsilyl (TMS), tert-butyldimethylsilyl (TBMDS),tert-butyldimethylsilyloxymethyl (TOM) or triisopropylsilyl (TIPS)ether), tetrahydropyranyl (THP), methyl ether and ethoxyethyl ether(EE). In many embodiments, the starting material may be benzindenetriol, i.e. compound of formula (1) with both R₁ and R₂ being H.

The first step may be alkylating compound of formula (1), suchbenzindene triol, with an alkylating reagent. In some embodiments, thealkylating reagent may have formula

wherein X may be a halogen, such as Cl, Br or I; R may be CN or COOR′,wherein R′ may be an alkyl group or substituted or unsubstituted benzyl.An alkyl group may be a saturated straight-chain or branched aliphaticgroup. For example, an alkyl group may a (C1-C6)alkyl, (C1-C5)alkyl,(C1-C4)alkyl or (C1-C3)alkyl. Examples of alkyl groups include methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,pentyl, iso-amyl, and hexyl. An alkyl group is optionally substitutedwith an alkyl, a cycloalkyl (e.g., cyclopentyl or cyclohexyl), an aryl(e.g., phenyl), or heteroaryl group. A substituted benzyl group may beoptionally substituted at one or more meta, ortho or para positions withone or more substituents, which may be independently selected from thegroup consisting of —NO₂, —CN, halogen (e.g., —F, —Cl, —Br or —I),(C1-C3)alkyl, halo(C1-C3)alkyl, (C1-C3)alkoxy and halo(C1-C3)alkoxy. Incertain embodiments, the substituted benzyl group may be para-methoxybenzyl or para-nitobenzyl.

As the result of the alkylating step, the following compound of formula(2) may be formed:

In some embodiments, the alkylating step may be performed in the presentof a base or a base salt, which may be, for example, lithium carbonate,potassium carbonate, sodium carbonate, cesium carbonate, calciumcarbonate, ammonium carbonate, lithium hydroxide, potassium hydroxide,magnesium hydroxide, barium hydroxide, sodium hydroxide, calciumhydroxide.

In some embodiments, a solvent for the alkylating step may be a polaraprotic solvent such as acetone, butanone, tetrahydrofuran,tetriarybutyl methyl ether, ethyl acetate or a combination thereof.

In some embodiments, the alkylating step may be performed without acatalyst. Yet in some other embodiments, the alkylating step may beperformed in the presence of an alkylation catalyst, which may be, forexample, tetrabutyl ammonium bromide, potassium iodide or sodium iodide.

In some embodiments, the second step may be hydrolysis of the product ofthe alkylating step, such as compound of formula 2. In certainembodiments, the hydrolysis may be followed by isolation and/orcrystallization of the product of hydrolysis from an appropriatesolvent. The product of hydrolysis may be treprostinil salt

or treprostinil as a free acid. The hydrolysis may be performed byreacting the product of the alkylating step, such as compound of formula2, with a solution, which may comprise one or more of hydroxide or abasic salt, such as carbonate. The hydroxide may be, for example,ammonia hydroxide or a metal hydroxide. The metal hydroxide may be, forexample, a hydroxide of Group IA or Group IIA solution. In certainembodiments, the metal hydroxide may be a hydroxide of K, Ca, Mg, Ba,Cs, Li or Na. In some embodiments, the basic salt may be, for example, acarbonate, such as lithium carbonate, potassium carbonate, sodiumcarbonate, cesium carbonate, calcium carbonate or ammonium carbonate.

In some cases, a solvent for the hydrolysis and a solvent for theisolation and/or crystallization step may the same, but in other cases,they may be different. Such solvent(s) may be an organic solventselected from ethanol, isopropyl alcohol, methanol, acetone, ethylacetate, hexanes, heptanes, isopropyl acetate or combinations thereof.

In some embodiments, when R′ is substituted or unsubstituted benzylgroup, the second step may be hydrogenalyzation of the alkylationproduct, such as compound of formula 2. The hydrogenalyzation of thealkylation product may be performed using a hydrogenation catalyst, suchas Pd catalyst on Carbon, in presence of hydrogen. The hydrogenalyzationmay be performed in an alcoholic solvent, such as ethanol, methanol orisopropyl alcohol. As the result of the hydrogenalyzation, the benzylgroup may be cleaved, thereby forming a “raw” mixture comprisingtreprostinil as a free acid. In some embodiments, the “raw” mixture maybe filtered and evaporated to form solid treprostinil. Yet in someembodiments, the raw mixture may be treated with a base, such as ahydroxide, or a base salt, such as a carbonate, to form treprostinilsalt, which may be isolated and/or crystallized.

In some embodiments, if treprostinil as a free acid is isolated as anintermediate, it may be then converted to its salt form using anappropriate base or a base salt, which may be one or more of hydroxideor carbonate, such as the ones discussed above. In one embodiment,treprostinil may be formed in situ and contacted with a base or a basesalt to form a new salt of treprostinil. In one embodiment, treprostinilis contacted with a base or a base salt to form a new salt oftreprostinil.

In some embodiments, the synthesis process may involve passing throughmultiple, i.e. more than 1, stages for either or both of treprostinil asa free acid and treprostinil salt. For example, as the result ofhydrolysis or hydrogenolysis treprostinil as a free acid may be formed,which may be converted to a salt, which then may converted back totreprostinil as a free acid, which may have higher purity that theearlier treprostinil. Also, a formed treprostinil salt may be convertedto treprostinil as a free acid, which may be converted to a new salt,which may be the same or different from the original salt. Treprostinilor treprostinil salt during each stage may or may not be isolated and/orcrystallized before a subsequent conversion.

FIG. 1 illustrates certain embodiments includes for synthesistreprostinil salts. The synthesis of salt is a two or three step processstarting from benzindene triol: 1) the first step is the O-alkylation ofbenzindene triol (1) with various alkylating reagents as shown in FIG.1; 2) the second step is the optional hydrolysis of the nitrileintermediate (6) or ester intermediates (7), (8) and (9) by using alkalimetal bases followed by isolation and crystallization of the salt froman appropriate solvent such as one of ethanol, isopropyl alcohol,methanol, acetone, ethyl acetate, hexanes, heptanes, isopropyl acetateor a combination thereof. In some cases, the solvent system for bothreaction step and recrystallization step are same, but in other casesthey may be different; 3) if treprostinil as a free acid is beingisolated as an intermediate then convert it back to its salt form usingappropriate base as described in FIG. 1. In one embodiment, treprostinilis formed in situ and contacted with the base salt to form the new saltof treprostinil. In one embodiment, treprostinil is contacted with thebase salt to form the new salt of treprostinil

The methods embodied herein allow for the formation of treprostinil ortreprostinil salt with reduced or simplified purification. In oneembodiment, treprostinil salt may be formed from compound of formula 1,such as benzindene triol, without any intermediate purification and/orisolation of treprostinil as a free acid. In one embodiment, acomposition comprising treprostinil as a free acid and at least oneimpurity is contacted with the base salt to form the new salt oftreprostinil to form a substantially pure new salt of treprostinil. Insome embodiments, the new salt of treprostinil is isolated asapproximately 99.0, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, 99.9or 99.95 percent pure.

The present salts may have an impurity profile different thantreprostinil materials produced by prior art methods. For example, thepresent salts may have a lower concentration of one or more oftreprostinil impurities, such as any of 1AU90, 2AU90 and 3AU90, whichare stereoisomers of treprostinil (UT-15); triol (which could be aprocess impurity or a degradation product); methyl ester and ethyl ester(process impurities), respectively; and 750W93 and 751W93 (two dimers oftreprostinil where the acid group of one molecule esterifies with analcohol on another molecule of UT-15). In some embodiments, the new saltof treprostinil does not comprise one or more of the listed impuritiesin a detectable amount.

In some embodiments, the methods allow for the production of asubstantially pure salt of treprostinil from the triol (1) withoutintermediate purification steps. The yield of the salt from the triol(1) may be greater than 70%, or greater than 75%, or greater than 80%,or greater than 85%, or greater than 90%.

Pathway 1, Pathway 2 or Pathway 3): Triol (1) may be alkylated usingvarious an alkylating reagent such as

which may be halo acetonitrile (2), methyl bromoacetate (3), ethylbromoacetate (4) and benzyl bromoacetate (5) etc. in the presence of abase or base salt, such as potassium carbonate, cesium carbonate,lithium hydroxide etc. The O-alkylation of the phenolic hydroxyl groupof triol (1) may be carried out, for example, with 1-1.2 equivalents ofthe alkylating agent in presence of 1-3 equivalents of the base or a thebase salt in a solvent, such as acetone, butanone, tetrahydrofuran,tertiarybutyl methyl ether, ethyl acetate. This O-alkylation may becarried with or without catalyst such as tetrabutyl ammonium bromide,potassium iodide or sodium iodide etc. Alkylation with haloacetonitrile(2) may provide nitrile intermediate (6) which may be carried forward tohydrolysis (step 6→40) without any further chromatographic purification.Similarly, the O-alkylation of triol (1) may be performed using anacetate, such as methyl bromoacetate (3), ethyl bromoacetate (4) andbenzyl bromoacetate (5) there by providing ester in the form penultimateintermediates (7, 8 and 9) of treprostinil. These ester intermediates(7, 8 and 9) may be carried forward for hydrolysis without any furtherchromatographic purification. The ester intermediate 9 bearing a benzylgroup may be hydrogenolysed using Palladium catalyst on carbon inpresence of hydrogen in an alcoholic solvent, such as ethanol, methanol,and isopropyl alcohol. The whole process may be simplified by the factthat after the benzyl group may cleave during the hydrogenationcondition (step 6→40) the alcoholic solution of reaction mixturecontaining treprostinil (UT-15) in the form of a free acid is filteredand evaporated to obtain treprostinil (UT-15) or this may be treatedwith) 0.5 to 1 equivalent of a base or a base salt, such as potassiumhydroxide, calcium hydroxide, sodium hydroxide, barium hydroxide, cesiumhydroxide, lithium hydroxide. This telescoping of the steps may lead toa process as shown in FIG. 4.

In the pathways 1, 2 and 3 the intermediates 6, 7, 8 and 9 after mayprovide treprostinil or its salt form (10) depending on the base usedduring hydrolysis and its isolation during the process. The pathwaysdiscussed above may be schematically represented as follows:

Pathway 1:

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Experimental Steps may include: 1) O-Alkylate the triol and carry thenitrile intermediate as such without purification to next step forhydrolysis.

2) Hydrolyze the ester intermediate and isolate as a salt form.

3) Crystallize to obtain the pure salt form.

Pathway 2:

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Experimental Steps may include 1) O-Alkylate the triol and carry theester intermediate as such without purification to next step forhydrolysis. The ester intermediate “R” is not necessarily limited to Meand Et, but rather any suitable ester known in the art may be used. Forexample, R may be C₁-C₁₂ alkyl or a C₁-C₆ alkyl. R may be optionallysubstituted by one or more organic moieties that are compatible with theconditions of the base hydrolysis step.

2) Hydrolyze the ester intermediate and isolate as salt form.

3) Crystallize to obtain the pure salt form.

Pathway 3:

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Experimental Steps: 1) O-Alkylate the triol and carry the esterintermediate as such without purification to next step forhydrogenolysis.

2) Hydrogenolyze the ester intermediate and carry the alcoholicsolution, such as a methanol or ethanol solution, of acid for treatmentwith base and form the salt. Or the ester may be hydrolyzed with base toobtain the salt form of treprostinil. The benzyl ether may be optionallysubstituted benzyl. Alternatively, the benzyl may instead be anoptionally substituted aryl moiety.

3) Crystallize to obtain the pure salt form.

In one embodiment, the salt of UT-15 demonstrates at least one of thefollowing improved properties: improved solubility, desired biologicalactivity, chemically-stable solid form and a solid form that is stablein a solid-dose formulation.

The present application also provides a number of novel treprostinilsalts including potassium salt of treprostinil; !-arginine salt oftreprostinil, l-lysine salt of treprostinil, N-methylglucamine salt oftreprostinil; choline salt of treprostinil; magnesium salt oftreprostinil; ammonium salt of treprostinil; calcium salt oftreprostinil and tromethamine salt of treprostinil. In some embodiments,the salt of treprostinil may be in a crystalline solid form. Yet in someembodiments, the salt of treprostinil may in an amorphous solid form.Yet in some embodiments, the salt of treprostinil may be a mixture of atleast one crystalline solid form and an amorphous solid form. A purityof the salt in the solid form may be at least 98.0%; at least 98.5%; atleast 98.8%; at least 99%; at least 99.1%; at least 99.2%; at least99.3%; at least 99.4%; at least 99.5%; at least 99.6%; at least 99.7%;at least 99.8%; or at least 99.9% or at least 99.95%. The novel saltsmay be produced in large quantities, such as of at least 20 g or atleast 30 g or at least 40 g or at least 50 g or at least 60 g or atleast 70 g or at least 80 g or at least 90 g or at least 100 g or atleast 110 g or at least 120 g or at least 130 g or at least 140 g or atleast 150 g or at least 160 g or at least 170 g or at least 180 g or atleast 190 g or at least 200 g.

One or more salt disclosed in this application may be used for preparinga pharmaceutical formulation together with one or more pharmaceuticallyacceptable excipient or additive. Suitable additives or excipientsinclude, but not limited to, sucrose, lactose, cellulose sugar,mannitol, maltitol, dextran, sorbitol, starch, agar, alginates, chitins,chitosans, pectins, tragacanth gum, gum arabic, gelatins, collagens,casein, albumin, synthetic or semi-synthetic polymers or glycerides,methyl cellulose, hydroxypropylmethyl-cellulose, and/orpolyvinylpyrrolidone. In some embodiments, while being dissolved in anappropriate solvent one or more salts may be used for preparing atreprostinil formulation for administering via subcutaneous,intravenous, oral or inhalation route.

In some embodiments, one or more of the present salts in a solid formmay also be used for preparing a solid dosage oral form, such as apowder, a granule, a tablet, a pellet, a pill, a capsule, a gelcap, anda caplet, for oral administering. Optionally, the oral dosage form maycontain one or more other ingredients to aid in administration, such asan inactive diluent, or a lubricant, such as magnesium stearate, or apreservative, such as paraben or sorbic acid, or an anti-oxidant, suchas ascorbic acid, tocopherol or cysteine, a disintegrating agent, abinders, a thickener, a buffer, a sweetener, a flavoring agent or aperfuming agent. Additionally, one or more of dyestuffs or pigments maybe added for identification. Tablets may be further treated withsuitable coating materials known in the art.

The invention is further illustrated by, though in no way limited to,the following examples.

EXPERIMENTAL EXAMPLES Example 1: Preparation of UT-15D-Potassium Salt

Treprostinil potassium salt was made by adding treprostinil (UT-15) topotassium hydroxide ethanol solution, followed by in two differentsolvents: acetone or ethyl acetate. The experiment was carried out ineach solvent system (ethanol/acetone and ethanol/ethyl acetate) withdifferent ratio to find the best condition to make the target compound.The results showed that ethanol/ethyl acetate is a better solvent systemthan ethanol/acetone, comparably. As can be seen in the table 1 and 2,when the volume of acetone or ethyl acetate increased, the yield ofUT-15 potassium salt also increased accordingly, until the yield reachedto the peak at about 80%. Overall, the reaction condition atethanol/ethyl acetate ratio 1/10 is easy to work with, in term ofsolvent boiling point, volume and yield of product (−80%). Based on theresults of the reaction in ethanol and ethyl acetate, an experiment witha larger scale of ˜(40 g) was carried out. The results confirmed theabove findings. The melting point of the UT-15 potassium salt was about180° C. in both ethanol/acetone and ethanol ethyl acetate cases. Thestructure of UT-15 potassium was confirmed by QC analytical data andother spectral data.Scheme 1 presents the flow chart of synthesis:

Part One: Condition Study

In this part of the experiment, UT-15 potassium salt was synthesizedfrom two different solvent systems, ethanol/acetone and ethanol/ethylacetate. The experiment was carried out with different ratios betweenethanol and acetone, and between ethanol and ethyl acetate, to find thebest solvent condition for the reaction.

a. Ethanol and Acetone

To a clear solution of potassium hydroxide (1 eq.) in ethanol (5 mL) ina round bottom flask, was added UT-I5 (1 eq.). The mixture was stirredat room temperature for about 10 minutes until a clear solution wasobtained. Then acetone was added to the ethanol solution while stirring.The stirring was stopped when white solid started coming out from thesolution. The mixture was left at room temperature overnight. The solidwas collected by filtration. It was washed with acetone and then driedat 70° C. under vacuum for 4 hours. See the detail results in Table 1and in FIG. 2.

TABLE 1 Results of UT-15 potassium salt in ethanol and acetone Lot #UT-15/KOH Eq. Acetone/EtOH M.P. ° C. Yield, % D-1026-046 0.812 g/0.117 g1.0/1.0 30 mL/5 mL (6/1) 178.5-179.5 56.1 D-1026-047 0.710 g/0.102 g1.0/1.0 50 mL/5 mL (10/1) 178.0-179.0 66.7 D-1026-049 0.853 g/0.122 g1.0/1.0 75 mL/5 mL (15/1) 177.8-179.0 68.4 D-1026-051 0.723 g/0.104 g1.0/1.0 100 mL/5 mL (20/1) 179.0-180.2 78.1 D-1026-085 0.730 g/0.105 g1.0/1.0 125 mL/5 mL (25/1) 179.0-181.0 83.6

b. In Ethanol and Ethyl Acetate

To a clear solution of potassium hydroxide (1 eq.) in ethanol (5 mL) ina round bottom flask, was added UT-15 (1 eq.). The mixture was stirredat room temperature for about 10 minutes until a clear solution wasobtained. Then ethyl acetate was added to the ethanol solution whilestirring. The stirring was stopped when white solid started coming outfrom the solution. The mixture was left at room temperature overnight.The solid was collected by filtration. It was washed with ethyl acetateand then dried at 70° C. under vacuum for 3 hours. See the detailresults in Table 2 and in FIG. 3.

TABLE 2 Results of UT-15 potassium salt in ethanol and ethyl acetate Lot# UT-15/KOH Eq. EtOH/Ethyl Acetate M.P. ° C. Yield, % D-1026-056 0.870g/0.125 g 1.0/1.0 5 mL/25 mL (1/5) 177.0-178.5 55.5 D-1026-059 0.799g/0.115 g 1.0/1.0 5 mL/50 mL (1/10) 179.5-180.8 79.8 D-1026-062 0.771g/0.111 g 1.0/1.0 5 mL/75 mL (1/15) 178.5-180.0 81.5 D-1026-086 1.100g/0.158 g 1.0/1.0 5 mL/100 mL (1/20) 179.0-180.5 82.8 D-1026-087 0.998g/0.143 g 1.0/1.0 5 mL/125 mL (1/25) 179.1-180.2 83.1

Part Two: Preparation of Treprostinil (UT-15) Potassium Salt (40 gScale)

Table 3 provides materials used in the synthesis:

TABLE 3 Reagents MW Amount Mole Eq. UT-15 390.52 40.23 g 0.103 1.00 KOH56.11 5.78 g 0.103 1.00 Ethanol — 250 mL — — Ethyl Acetate — 2500 mL — —To a 5-L round bottom flask, potassium hydroxide and ethanol were added.It was stirred at room temperature until it was clear. To the potassiumethanol solution, was added UT-15.The reaction mixture was stirred at room temperature about 30 minutesuntil it was clear. The mixture was then added ethyl acetate slowlywhile stirring. The stirring was stopped when white solid started tocome out of the solution. The reaction mixture was allowed at roomtemperature overnight. The solid was filtered, washed with ethyl acetate(500 mL), dried at 70° C. under vacuum for 6 hours to give the product(35.12 g, 79.5%).Table 4 presents analytical data.

TABLE 4 Melting point 180.0-182° C. IR Consistent with Structure ¹H NMRConsistent with Structure ¹³C NMR Consistent with Structure Purity(HPLC) 99.1% Elemental Analysis Carbon Hydrogen 66.47% (Found) 7.75%(Found) 66.45% *Theory) 7.76% (Theory

Example 2: UT-15-Calcium Salt and Tromethamine Salts

Summary. The objective of was to develop synthetic methods for thesynthesis of new salts of UT-15 and produce at least 50 g of each salt.Present report describes the synthesis of two new salts of UT-15:calcium and tromethamine salts.

For these new salts, analytical data: ¹H-NMR, 13C-NMR, IR, purity byHPLC, DSC data, TGA data, water contents, specific rotation werecollected.

Treprostinil (UT-I5) is benzindene prostacyclin containing carboxylicacid moiety. Various bases (organic and inorganic) were considered forthe synthesis of new salts of UT-15. Present report uses two bases:calcium hydroxide (inorganic base) and tromethamine (organic base).Synthesis of these salts is a two step process. First step involved thereaction of UT-IS (carboxylic acid moiety) and base in appropriatesolvent system, and second step was the recrystallization of salt fromappropriate solvent system. Details of these steps are given inexperimental section.

Calcium Salt

TABLE 5 Summary of materials used for synthesis of UT-15 calcium salt.Name MW Amount Eq UT-15 390.52 60 g 1 Calcium hydroxide 74 5.40 0.5 EtOH— 600 mL — Water — 1800 mL —A 3000-mL, three-necked, round-bottom flask equipped with a mechanicalstirrer, thermometer and condenser was charged with UT-15 (60 g), andethanol (600 mL). Mixture was heated at 75-80° C. until clear. To theclear solution calcium hydroxide (5.40 g) was added in two portions. Thereaction mixture was stirred and heated to 70-80° C. to obtain a clearsolution (˜1 h). Water (1800 mL) was added slowly keeping thetemperature of solution at 75-80° C. After complete addition of water,the solution was allowed to cool to ambient temperature overnight whilestirring. The product was filtered, washed with water and dried undervacuo for 1 h. The product was transferred from the Buchner funnel to aglass and dried over night in a fume hood. Finally the product wasfurther dried under high vacuum at 50-55° C. for 6 hours (50.2 g, mp.154-160° C.Table 6 provides data for calcium salt.

TABLE 6 Structure

Amount 50 g Lot number D-1055-077-1 Molecular formula C₄₆H₆₈CaO₁₁ MW837.12 Appearance Off white ¹H NMR Consistent with structure ¹³C NMRConsistent with structure Purity (HPLC) 98.9% Melting point 154-160° C.

Tromethamine Salt

TABLE 7 Summary of materials used for synthesis of UT-15 tromethaninesalt. Name MW Amount Eq UT-15 390.52 54.55 g 1.00 Tromethanine 121.1417.06 1.00 Isopropanol (IPA) — 330 mL — MTBE — 1500 mL — Water — 15 mL —A 3000-mL, three-necked, round-bottom flask equipped with a mechanicalstirrer, thermometer and condenser was charged with UT-15 (54.55 g),isopropanol (330 mL), and water (15 mL) and was heated at 50-55° C.until clear solution was obtained, then tromethamine (17.06 g) wasadded. The reaction mixture was heated to 60° C. while stirring toobtain a clear solution. To his clear solution methyl t-butyl ether(MTBE) was added slowly keeping the temperature between 50-55° C. Aftercomplete addition of MTBE, the solution was allowed to cool to ambienttemperature overnight while stirring. The product was filtered, washedwith water and dried under vacuo for 1 h. The product was transferredfrom the Buchner funnel to a glass tray and dried over night in a fumehood. Finally the product was dried under high vacuum at 45-48° C. for 4hours (55.4 g, mp. 68-71° C.). Table 8 provides data for tromethaminesalt.

TABLE 8 Structure

Amount 50 g Lot number D-1051-023 Molecular Formula C₂₇H₄₅NO₈ MolecularWeight 511.66 Appearance White Solid ¹HNMR Consistent with structure ¹³CNMR Consistent with structure Purity (HPLC) 99.93% Melting point 66-71°C. Elemental analysis Required C = 63.38, H = 8.86, N = 2.74 Required ifas monohydrate: C = 61.23, H = 8.94, N = 2.64 Found: C = 60.54, H =8.98, N = 2.63 Water content 4.4% w/w Specific rotation +32.4° @589 nmand 25° C. c = 1.0256 g/l00 mL in MeOH

Example 3: Synthesis of Alternate Treprostinil Salts

The objective was to develop new methods for the synthesis of alternatesalts of UT-15 and to produce at least 200 mg of each salt for thedissolution studies. Total seven salts of UT-15 have been prepared:

1. UT-15-L-Arginine salt

2. UT-15-L-Lysine salt

3. UT-15-N-Methylglucamine salt

4. UT-15-Choline salt

5. UT-15-Potassium salt

6. UT-15-Magnesium salt

7. UT-15-Ammonium salt

For all new UT-15 salts, analytical data: IH-NMR, 13C_NMR, IR, purity byHPLC, DSC data, TGA data, water contents, specific rotation werecollected.

Since UT-15 is benzindene prostacyclin containing carboxylic acid,various bases were considered for the synthesis of new salts of UT-15.This study used UT-15 with seven bases, which include four organic basesand three inorganic bases. Four organic bases were: L-arginine,L-lysine, N-methylglucamine, and choline hydroxide. Other threeinorganic bases include potassium hydroxide, ammonia gas, and magnesiumhydroxide. Synthesis of salts was a two step process. First step was thereaction of UT-15 (carboxylic acid) and base in appropriate solventsystem, and second step. was the recrystallization of salt fromappropriate solvent system. In some cases, the solvent system for bothreaction step and recrystallization step was same, but in other cases itwas different. Details of these steps were given in experimentalsection. In few cases, the purpose of addition of small amount of waterwas to avoid synthesis of ester of UT-15 with alcoholic solvent, whenthe mixture was heated to greater than 50° C.

Arginine Salt

Name MW Amount Eq UT-15 390.52 4.50 g 1.00 L-Arginine 174.20 2.01 g 1.002-propanol — 135 mL — Water — 10 mL — Ethyl Acetate — 250 mL —

Table 9 provides a summary of materials used in the synthesis.

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15-L-Arginine salt (17.01g), ethanol (200 mL). The mixture was heated to 70-80° C. whilestirring. At this temperature, water (3 mL) was added slowly to obtain aclear solution. After complete addition of water, the solution wasallowed to cool slowly to ambient temperature. The product was isolatedby filtration and washed with ethanol. The product was transferred fromthe Buchner funnel to a glass container for air-drying over night in afume hood. The product (lot D-1041-011) was dried under high vacuum at70-75° C. for 16 hours. Table 10 provides data for the arginine salt.

TABLE 10 Structure

Lot number D-1029-034 Molecular formula C₂₉H₄₈N₄O₇ MW 564.72 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.12% Melting Point 183-184° C. Melting point(DSC) 182.04° C. IR Consistent with structure Elemental analysisRequired: C = 61.68, H = 8.57, N = 9.92 Found: C = 61.31, H = 8.55, N =9.62 TGA Moisture = 2.07, degradation beyond 200° C. Water content 0.53%w/w Specific rotation +35.8° @589 nm and 25° C.

L-Lysine Salt

Name MW Amount Eq UT-15 390.52 4.50 g 1.00 L-lysine 146.19 1.685 g 1.002-propanol — 108 mL — Water — 9 mL — Ethyl Acetate — 225 mL —

Table 11 provides summary of materials used in the synthesis

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15 (4.5 g), 2-propanol(108 mL), water (9 mL), and L-lysine (1.685 g). The reaction mixture wasstirred and heated to 70-80° C. to obtain a clear solution. At thistemperature, ethyl acetate was added slowly keeping the temperature ofsolution higher than 55° C. After complete addition of ethyl acetate,the solution was allowed to cool to 45° C. during 1-2 hours, then to 35°C. for one hour, and then to 25° C. for an addition one hour. At ambienttemperature, the product was isolated by filtration; product was washedwith ethyl acetate. The product was transferred from Buchner funnel to aglass container for air-drying over night in a fume hood. The productwas dried further under high vacuum at 50-55° C. for 4-5 hours. Table 12provides data for L-lysine salt.

Structure

Lot number D-1029-032 Molecular formula C₂₉H₄₈N₂O₇ MW 536.71 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.68% Melting Point 106° C. Melting point (DSC)97.43° C. IR Consistent with structure Elemental analysis Required: C =64.90, H = 9.01, N = 5.22 Found: C = 60.90, H = 9.04, N = 4.85 TGA Noweight loss due to moisture; loss due to degradation beyond 200° C.Water content 6.7% w/w Specific rotation +36.3° @589 nm and 25° C.

N-Methylglucamine Salt

Name MW Amount Eq UT-15 390.52 4.00 g 1.00 N-methylglucamine 146.19 2.00g 1.00 2-propanol — 60 mL — Water — 0.8 mL — MTBE — 120 mL — Hexanes —40 mL —

Table 13 provides a summary of materials used in the experiments

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15 (4.0 g), 2-propanol(108 mL), water (0.8 mL), and N-methylglucamine (2.00 g). The reactionmixture was stirred and heated to 70-80° C. to obtain a clear solution.At this temperature, MTBE (120 mL) was added slowly keeping thetemperature of solution higher than 55° C., followed by hexanes (40 mL).After complete addition of MTBE and hexanes, the solution was allowed tocool to 45° C. during 1-2 hours, then to 35° C. for one hour, and thento 25° C. for an additional 30 minutes. At ambient temperature, theproduct was isolated by filtration and washed with MTBE/hexanes (1:1).The product was transferred from Buchner funnel to a glass container forair-drying over night in fume hood. The product was dried further undervacuum at 50-55° C. for 4 hours. Table 14 provides results forN-methylglucamine salt.

TABLE 14 Structure

Lot number D-1029-036 Molecular formula C₃₀H₅₁NO₁₀ MW 585.74 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.51% Melting Point 82-83° C. Melting point(DSC) 72.96° C. IR Consistent with structure Elemental analysisRequired: C = 61.52, H = 8.78, N = 2.39 Found: C = 59.77, H = 8.78, N =2.34 TGA Weight loss due to moisture up to 100° C.; loss due todegradation beyond 150° C. Water content 3.3% w/w Specific rotation+19.4° @589 nm and 25° C.

Mg Salt

Name MW Amount Eq UT-15 390.52 5.75 g 1.00 Magnesium Hydroxide 58.330.439 g 0.5 Ethanol — 172 mL — Water — 55 mL — MTBE — 86 mL — Hexanes —30 mL —

Table 15 provides summary of materials used in the experiment.

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15 (5.75 g), ethanol (86mL), water (55 mL), and magnesium hydroxide (439 mg). The reactionmixture was stirred and heated to 70-80° C. to obtain a clear solution.The solution was filtered to remove any insoluble foreign particles. Thefiltrate was evaporated under vacuum to give a gummy material. The gummymaterial was dissolved in ethanol (86 mL) by heating to 70-80° C. Atthis temperature, MTBE (86 mL) was added slowly keeping the temperatureof solution higher than 55° C., followed by hexanes (30 mL). Aftercomplete addition of MTBE and hexanes, the solution was allowed to coolto 45° C. during 1-2 hours, then to ambient temperature overnight. Atambient temperature, the product was isolated by filtration and washedwith MTBE. The product was transferred from Buchner funnel to a glasscontainer for air-drying over night in fume hood. The product was driedfurther under vacuum at 50-55° C. for 4 hours. Table 16 provides datafor the magnesium salt.

TABLE 16 Structure

Lot number D-1029-038 Molecular formula C₂₃H₃₃MgO₅ MW 413.82 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.68% Melting Point 80-81.5° C. Melting point(DSC) 75.77° C. IR Consistent with structure Elemental analysisRequired: C = 66.76, H = 8.04 Found: C = 66.90, H = 8.29 TGA No weightloss due to moisture; loss due to degradation beyond 250° C. Watercontent 13.1% w/w Specific rotation +44° @589 nm and 25° C.

Potassium Salt

Name MW Amount Eq UT-15 390.52 4.00 g 1.00 Potassium Hydroxide 56.110.575 g 1.00 2-propanol — 40 mL — Water — One drop — MTBE — 25 mL —Hexanes — 85 mL —

Table 17 provides a summary of materials used in the experiment.

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15 (4.00 g), 2-propanol(40 mL), water (one drop), and potassium hydroxide (575 mg). Thereaction mixture was stirred and heated to 70-80° C. to obtain a clearsolution. At this temperature, MTBE (25 mL) was added slowly keeping thetemperature of solution higher than 55° C., followed by hexanes (85 mL).After complete addition of MTBE and hexanes, the solution was allowed tocool to 45° C. during approximately 16 hours, then to ambienttemperature. At ambient temperature, the product was isolated byfiltration and washed with MTBE. The product was transferred fromBuchner funnel to a glass dish for air-drying overnight in fume hood.The product (lot D-1 029-041) was dried further under vacuum at 50-55°C. for 4 hours. Table 18 provides data for the potassium salt.

TABLE 18 Structure

Lot number D-1029-041 Molecular formula C₂₃H₃₃KO₅ MW 428.61 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.39% Melting Point 180-181° C. Melting point(DSC) 177.37° C. IR Consistent with structure Elemental analysisRequired: C = 64.45, H = 7.76 Found: C = 64.42 H = 7.77 TGA No weightloss due to moisture; loss due to degradation beyond 250° C. Watercontent 0.3% w/w Specific rotation +39.5° @589 nm and 25° C.

Ammonium Salt

Name MW Amount Eq UT-15 390.52 4.00 g 1.00 Ammonia (gas) 17.03 — —2-propanol — 50 mL — MTBE — 75 mL — Hexanes — 75 mL —

Table 19 provides summary of materials used in the experiment

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15 (4.00 g), 2-propanol(40 mL). The mixture was stirred and heated to 40-45° C. to obtain aclear solution. Allow the temperature of the solution to cool to 30-35°C., and then bubble the ammonia gas through the solution for 45 minutes.Ammonia gas inlet was removed, and hexane (75 mL) was added and allowedthe mixture to stir overnight at ambient temperature. At ambienttemperature, the product was isolated by filtration; product was washedwith MTBE/hexanes (1:1). The product was transferred from Buchner funnelto a glass dish for air-drying over night in fume hood. The product (lotD-1029-043) was dried further under vacuum at 50-55° C. for 4 hours.Table 20 provides data for the ammonium salt.

TABLE 20 Structure

Lot number D-1029-043 Molecular formula C₂₃H₃₇NO₅ MW 407.55 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.52% Melting Point 75-76° C. Melting point(DSC) 69.42° C. IR Consistent with structure Elemental analysisRequired: C = 67.78, H = 9.15, N = 3.44 Found: C = 67.24, H = 9.13, N =2.76 TGA 4% weight loss due to moisture up to 100° C.; continuous lossdue to degradation beyond 100° C. Water content 4.6% w/w Specificrotation +41.4° @589 nm and 25° C.

Choline Salt

Name MW Amount Eq UT-15 390.52 4.00 g 1.00 Choline hydroxide 121.18 3.1g 1.0 (45% wt, MeOH) 2-propanol — 60 + 90 mL — MTBE — 115 mL —

Table 21 provides summary of materials used in the experiment.

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15 (4.50 g), 2-propanol(60 mL). The mixture was stirred and heated to 70-80° C. to obtain aclear solution. To the solution was added choline hydroxide (3.1 g) andstirred the mixture for short period. The solvent was evaporated undervacuum to give a gummy material. The gummy material was dissolved in2-propanol (90 mL) by heating to 70-80° C. At this temperature, MTBE(115 mL) was added slowly keeping the temperature of solution more than55° C. After complete addition of MTBE, the solution was allowed to coolto 50° C., then to 40° C. and to ambient temperature overnight. Atambient temperature, the product was isolated by filtration; product waswashed with MTBE/hexanes (1:1). The product was transferred from Buchnerfunnel to a glass container for air-drying over night in fume hood. Theproduct was dried further under vacuum at 50-55° C. for 4 hours. Table22 provides data for the choline salt.

TABLE 22 Structure

Lot number D-1029-045 Molecular formula C₂₈H₄₇NO₆ MW 493.68 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.36% Melting Point 163-164 °C. Melting Point(DSC) pending° C. IR Consistent with structure Elemental analysisRequired: C = 68.12, H = 9.60, N = 2.84 Found: C = 67.76, H = 9.69, N =2.83 TGA No weight loss due to moisture; loss due to degradation beyond150° C. Water content 0.9% w/w Specific rotation +34.2° @589 nm and 25°C.

Example 4: Synthesis of Potassium and L-Arginine Salts of Treprostinil

This example reports to the synthesis of two salts, potassium salt ofUT-15 (UT-15D) and L-Arginine salt of UT-15.

From synthetic point of view, the desired properties of UT-15 salts mayinclude better aqueous solubility, higher melting point, dense nature,and robust process. Two salts, UT-15D and UT-15-L-Arginine possess thedesired properties. Presently, potassium salt of UT-15 (UT-15D) wasprepared using ethanol and ethyl acetate. Initially, Arginine salt ofUT-15 was prepared and recrystallized using IPA/EtOAc/H₂O. Currently,IPA/H₂O and EtOH/H₂O solvent systems were used for recrystallization.The number of solvents for recrystallization was reduced (three to two).Ethanol is preferred over isopropanol for recrystallization, becauseisopropanol was not removed completely from UT-15-L-Arginine attemperature 70-75° C., under high vacuum for more than 45 hours, whereasethanol was removed within 16 hours under similar conditions.

Potassium Salt

Name MW Amount Eq Ratio UT-15 390.52 150.00 g 1.00 1.00 Potassiumhydroxide 56.11 21.55 g 1.00 NA Ethyl acetate NA 7500 mL NA 50.00 Ethanol NA 115 mL NA 5.00Table 23 provides summary of materials used for the potassium saltsynthesis.A 12-L, three-necked, round-bottom flask equipped with a mechanicalstirrer was charged with potassium hydroxide (21.55 g), ethanol (650 mL)at room temperature. The mixture was stirred to obtain a clear solution.UT-15 (150.00 g, solid) was added in portions to the solution ofpotassium hydroxide in ethanol at ambient temperature. After completeaddition of UT-15, the mixture was stirred for 30 minutes to obtain aclear solution. At ambient temperature, ethyl acetate (7500 mL) wasadded solution slowly keeping the solution clear. The clear solution wasallowed to stir gently at ambient temperature for 3-4 hours to obtain awhite solid. The product was isolated by filtration and washed withethyl acetate. The product was transferred from the Buchner funnel to aglass tray and air-dried in a fume-hood overnight. The product (lotD-1029-171) was dried further under vacuum at 60-65° C. for 7-8 hours togive UT-15D (133.0 g, yield 81%) Table 24 provides data for potassiumsalt.

TABLE 24 Structure

Lot number D-1029-166 Molecular formula C₂₃H₃₃KO₅ MW 428.61 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.9% Melting Point 182-183.5° C. IR Consistentwith structure

L-Arginine Salt

Name Amount Ratio Lot No. UT-15-L-Arginine salt 17.01 1.00 D-1041-006Ethanol (anhydrous) 200 mL 11.76 T-08-0186 Water  3 mL 0.176 Tap water

Table 25 provides summary of materials used in the L-arginine saltsynthesis.

A 500-mL, two-necked, round-bottom flask equipped with a magneticstirrer, and a thermometer was charged with UT-15-L-Arginine salt (17.01g), ethanol (200 mL). The mixture was heated to 70-80° C. whilestirring. At this temperature, water (3 mL) was added slowly to obtain aclear solution. After complete addition of water, the solution wasallowed to cool slowly to ambient temperature. The product was isolatedby filtration and washed with ethanol. The product was transferred fromthe Buchner funnel to a glass container for air-drying over night in afume hood. The product (lot D-1041-011) was dried under high vacuum at70-75° C. for 16 hours. Table 26 provides data for the L-arginine salt.

TABLE 26 Structure

Lot number D-1041-011 Molecular formula C₂₉H₄₈N₄O₇ MW 564.72 AppearanceWhite Solid ¹H-NMR Consistent with structure ¹³C-NMR Consistent withstructure Purity (HPLC) 99.87% Purity (HPLC, assay) 100.15% MeltingPoint 184-185° C. Elemental analysis Required: C = 61.68, H = 8.57, N =9.92 Found: C = 61.52, H = 8.71, N = 9.79 Specific rotation +36.6° @589nm and 25.2° C., and C = 1.0230

Although the foregoing refers to particular preferred embodiments, itwill be understood that the present invention is not so limited. It willoccur to those of ordinary skill in the art that various modificationsmay be made to the disclosed embodiments and that such modifications areintended to be within the scope of the present invention.

All of the publications, patent applications and patents cited in thisspecification are incorporated herein by reference in their entirety.

What is claimed is:
 1. A method of preparing a potassium salt oftreprostinil comprising: reacting treprostinil with potassium hydroxidein a solution comprising ethanol and ethyl acetate to form the potassiumsalt of treprostinil, wherein a volume ratio of ethanol:ethyl acetate inthe solution ranges from 1:25 to 1:5.
 2. The method of claim 1, whereinthe volume ratio of ethanol:ethyl acetate in the solution ranges from1:25 to 1:10.
 3. The method of claim 1, wherein the volume ratio ofethanol:ethyl acetate in the solution ranges from 1:15 to 1:10.
 4. Themethod of claim 1, wherein the volume ratio of ethanol:ethyl acetate inthe solution is 1:10.
 5. The method of claim 1, wherein said reactingcomprises contacting treprostinil with a solution of potassium hydroxidein ethanol followed by adding ethyl acetate.
 6. The method of claim 1,further comprising stirring the solution until a solid starts coming outof the solution.
 7. The method of claim 6, further comprising collectingthe solid.
 8. The method of claim 7, wherein said collecting isperformed by filtrating the solution.
 9. The method of claim 7, furthercomprising washing and drying the collected solid.
 10. The method ofclaim 9, wherein said washing is washing with ethyl acetate.
 11. Themethod of claim 9, wherein said drying is vacuum drying.
 12. The methodof claim 9, wherein the dried solid has a melting temperature rangingfrom 178.5° C. to 182.0° C.
 13. The method of claim 10, wherein thedried solid has a melting temperature ranging from 179.5° C. to 180.8°C.
 14. The method of claim 1, wherein a yield of said potassium salt isat least 79.8%.
 15. The method of claim 1, wherein at least 35.12 g ofthe potassium salt of treprostinil is produced.